Hereinafter, a description is made of a conventional transformer using the related drawings.
FIG. 11 is an exploded perspective view of a conventional transformer. In FIG. 11, bobbin 2 with primary winding 1 wound therearound has through hole 3; and bobbin 5 with secondary winding 4 wound therearound has through hole 6. Then, bobbin 2 has bobbins 5 arranged at both sides of bobbin 2.
Center leg 8 of E-shaped magnetic core 7 is inserted into through hole 3 of bobbin 2; outer leg 9 is inserted into through hole 6 of bobbin 5. After the front ends of center leg 8 and outer legs 9 are inserted into through holes 3, 6, center leg 8 and outer legs 9 are butt-joined to rod-shaped magnetic core 10 positioned facing E-shaped magnetic core 7 to form a transformer including a closed magnetic circuit. For instance, patent literature 1 is known as information on prior art documents related to this conventional transformer.
FIG. 12 is a first sectional view of a conventional transformer. In FIG. 12, magnetic flux φ1 generated at center leg 8 by primary winding 1 passes through closed magnetic circuit 11 composed of E-shaped magnetic core 7 and rod-shaped magnetic core 10. Then, magnetic flux φ1 is typically split into magnetic flux φ2 and φ3, exciting an equivalent voltage at secondary winding 4.
However, magnetic flux φ2 and φ3 is not evenly diverted when each impedance of loads (not shown) connected to secondary windings 4 fluctuates even if secondary windings 4 have the same winding specifications. That is to say, load fluctuation at one secondary winding 4 influences the other second secondary winding 4. This results in fluctuation of loads (not shown) at secondary windings 4 and fluctuation of magnetic flux φ2, φ3 interlinked at secondary windings 4 producing synergetic adverse affect. Consequently, with the loads (not shown) being discharge lamps, for instance, variation occurs in each brightness of the discharge lamps connected to one secondary winding 4 and the other.
FIG. 13 is a first sectional view of a conventional transformer. In FIG. 13, in a form of a transformer in which windings are arranged at both outer legs 9, center leg 8 is a common magnetic path between magnetic flux φ3 passing through one primary winding 1 and one secondary winding 4; and magnetic flux φ4 passing through the other primary winding 1 and the other secondary winding 4. In this case, when equal loads are connected to one secondary winding 4 and the other, magnetic flux φ3 and φ4 is equivalent and stabilized.
However, if the loads are not kept in equilibrium, magnetic flux φ3, φ4 cannot be maintained in balance, causing one secondary winding 4 to be subject to interference from the other magnetic flux φ4, and the other secondary winding 4 to be subject to interference from one magnetic flux φ3. Consequently, with the loads (not shown) being discharge lamps, for instance, variation occurs in each brightness of the discharge lamps connected to one secondary winding 4 and the other.
[Patent literature 1] Japanese Patent Unexamined Publication No. 2005-303103